things have been tasted, it's not that many," Mark Zoller, the company's head of research, told me. "Usually what people do is create derivatives of what they already know: if you have as- partame, you create neotame. We can go in completely from left field, with no preconceptions about what can be sweet. We have a library of two hun- dred and fifty thousand compounds, and we are creating new libraries all the time. We can throw it all at the recep- tor and let the results speak for them- selves." In the past four years, Senomyx has tested more than twenty million samples. Its sweetener program has identified the three most promising classes of chemicals, whittled those down to two candidates, and tinkered with them in the lab, adding some atoms for stability, some for potency. The final product won't be a new sugar substitute-"How many of those do we need?" Zuker says. It may not even have any taste. All it will do is amplify the taste of sugar. Taste potentiators, as they're called, are not entirely new to the food in- dustry. The ingredient list on a can of soup or a hunk of processed cheese sometimes includes a substance called IMP, a few entries below MSG, or monosodium glutamate. MSG is to umami what sugar is to sweet: the taste in its purest, most familiar form. IMP's singular virtue is its synergy with MSG. Like the sweet recep- tor, the umami receptor has multiple binding sites. IMP attaches to one spot, MSG to another; together, they fit so snugly that their effect is multi- plied. Add a little IMP to a soup with MSG in it, and the umami taste will increase roughly ten-fold. "It's like a hearing aid," Zoller told me. It turns up the volume. Senomyx has found four new umami potentiators in the course of its chemical trawling, all of them more effective than IMP, all recently de- clared safe by the F.D.A. (The first products containing them should ap- pear later this year.) The company's . ,. two sweet potentIators aren t qUIte as far along. The best one is known as Substance 951. If you add only a few parts per million of it to a soda, you can take out forty per cent of the sugar and the soda will taste as sweet. But Senomyx is still working on making it stronger and on improving or eliminat- ing its taste. (I wasn't allowed to try it.) Zoller says that the compound should be on the market by next year, but most consumers won't be aware of it. Like the newumami potentiators, Substance 951 will be used in such tiny quantities that it won't have to be listed on labels. Instead, it will join all the other "natu- ral and artificial flavors" that float through our foods, ignored by all but the most obsessive ingredient-watchers, and quietly do the work that sugar once did. W alking through the labs at Seno- myx, watching taste cells turn on and off in their little plastic wells, I was reminded of a wooden display case that I'd seen at NutraSweet. The case was fitted with three glass vials, all with different sweeteners measured in por- tions of equal strength. The first vial held forty grams of sugar and was nearly full. The second had a thin layer of as- partame-about a fifth of a gram. The last was labelled "neotame" and looked empty. I had to hold it up to the light to see the faint glimmer of powder inside. You cotÙd call this progress. The sweeter the chemical, the fewer of its molecules will wind up in our bloodstreams. And, if that chemical can also help curb obe- sity and diabetes, so much the better. 'We consume too many calories and we don't have to," Craig Petray told me. "If products can taste the same and have twenty-five or thirty per cent less sugar, h ' " t at s a start. The same argument, of course, has always been made for artificial sweet- eners. Like the dream of the paperless office or the superhighway that will untangle traffic for good, it presumes that there is a natural limit to our needs-that humanity's sweet tooth can be satisfied. Yet our sweet recep- tors evolved in environments with so little sugar that they may not have a shutoff point. Elizabeth Cashdan, an anthropologist at the University of Utah, has seen Mrican bushmen pick fruit apart for the barest trace of pulp. "And honey! What they will go through for a taste of honey is just in- credible," she says. A number of biologists have tried to gauge the depth of our appetite for sugar over the years. Newborns, they've found, are already fixated on sweetness. If you put some sugar on a latex nipple, an infant will suck it longer and harder than a plain nipple. Give her a drop of sweet water when she's crying and her heartbeat will slow, her face will relax, and her brain activity will fall into a "hedonically positive" pattern. (Hugs and pacifiers have a similar effect, but not as lasting.) According to the bio- logist Julie Mennella, at the Monell Chemical Senses Center, sugar seems to trigger the release of opiates in the brain, both bringing pleasure and block- ing pain. (When Mennella asked chil- dren to stick their hands in icy water, those with some sugar water in their mouths kept their hands in longer.) Adults who are offered drinks of dif- ferent sugar concentrations tend to reach a "bliss point" at about nine tea- spoons per cup-fifty per cent sweeter than the average soft drink. Children prefer eleven teaspoons per cup, and theyll take it even stronger. "For babies, the fundamental rule is: the sweeter the better," Monell's director, Gary Beau- champ, told me. "There is nothing that . " IS too sweet. Beauchamp has also tried to study the opposite tendency: the less sugar people eat, the less of a taste for it they have. He had to abandon the exper- iment, though, because his subjects couldn't stick to their sugar-free diets. (They were much better at abstaining from salt; and he did find that their ap- petite for it diminished.) The human palate is nothing if not adaptable, but it's hard to lose your craving for sugar when it's found in everything from wheat bread to spaghetti sauce to mac- aroni and cheese. Artificial sweeteners, far from diminishing that appetite, often seem to reinforce it. Americans ate about twenty-four pounds of sugar sub- stitutes per person last year, nearly dou- ble what they did in 1980, yet sugar consumption rose about twenty-five THE NEW YORKER, MAY 22, 2006 45